Fibres released during drying can remain in accessible parts of a combined machine and appear in a later load. The preceding textiles therefore matter as well as the current wash.
Understanding this situation
This differs from a washer suddenly creating an unknown material. Follow the model's specified lint-removal or cleaning sequence and consider separating lint-shedding items from fabrics that show fibres prominently.
A useful next step
Check accessible seals and permitted cleaning points when safe, without dismantling the machine. If large amounts persist or accompany a fault, report the sequence of loads. Avoid using stronger chemicals to treat a physical fibre problem without the relevant maintenance guidance.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.